Coding of telephone speech signals uses the long-term prediction to predict similarity of waveforms among pitch periods. Since it is highly likely that coding of telephone speech signals is used in wireless communications and the like, codes of a fixed length are used for coding of pitch prediction parameters τ and ρ. In lossless coding of audio signals, a method for making predictions using a correlation between separate samples is described in patent literature 1. The method is related to a high efficiency coding apparatus and high efficiency decoding apparatus and again, fixed-length coding is used for coding of a multiplier ρ and time lag parameter τ. Patent literature: Japanese Patent No. 3218630